HR
HR refers to human resources. HR is a series of options you can enable on a team in the game, based on the skill of the leader, to automatically manage education, hiring, complaints and salaries.
It is assumed to be abbreviated in the UI in most cases, so if you write it out as human resources every time, it might be cut off in a lot of places. It would be preferable to find an abbreviation or at least a very short-form of the word(s).